Automotive lamp

ABSTRACT

An automotive lamp is capable of controlling a light distribution pattern PTN based on an image captured by a camera unit. The automotive lamp is capable of switching between multiple control modes designed with different combinations of the spatial resolution of the light distribution pattern PTN and the update speed of the light distribution pattern PTN.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an automotive lamp.

2. Description of the Related Art

When driving at night or through a tunnel, an automotive lamp plays animportant role in supporting safe driving. However, in a case in which awide region ahead of a vehicle is illuminated with high light intensityprioritizing the driver's visibility, this leads to a problem ofimparting glare to a driver of a leading vehicle or a oncoming vehicle(which will be referred to as a “forward vehicle”) or a pedestrian aheadof the user's vehicle.

In recent years, the ADB (Adaptive Driving Beam) technique has beenproposed in which a light distribution pattern is dynamically andadaptively controlled based on the state of the surroundings of thevehicle. With the ADB technique, the presence or absence of a forwardvehicle or a pedestrian ahead of the vehicle is detected, and theillumination is reduced or turned off for a region that corresponds tosuch a vehicle or pedestrian thus detected, thereby reducing glareimparted to a driver of the forward vehicle or a pedestrian.

SUMMARY OF THE INVENTION

The present invention has been made in view of such a situation.Accordingly, it is an exemplary purpose of an embodiment of the presentinvention to provide an automotive lamp that is capable of forming alight distribution pattern that provides improved visibility. Also, itis another purpose of an embodiment of the present invention to providean automotive lamp that is capable of forming a light distributionpattern that allows an in-vehicle camera to easily detect a target.

As a result of investigating a lighting device that controls a lightdistribution based on image data of a forward area ahead of a vehiclecaptured by a camera, the present inventors have come to recognize thefollowing problem. Typically, such an automotive lamp is used mainly atnight. Accordingly, a dark target must be captured by the camera.

In a case in which an image of a dark field is captured with sufficientbrightness that allows an object to be detected, there is a need toraise the sensitivity of the camera. However, in a case of raising theintensity, this leads to degradation of the S/N ratio. In a case inwhich light distribution is controlled based on image data with a lowS/N ratio, the noise component of the image data has an effect on alight distribution pattern to be projected. This has the potential tocause degradation of visibility. It should be noted that such a problemis by no means within the scope of common and general knowledge of thoseskilled in this art.

The present invention has been made in view of such a situation.Accordingly, it is an exemplary purpose of an embodiment of the presentinvention to provide an automotive lamp that is capable of forming alight distribution pattern with reduced noise effects.

An embodiment of the present invention relates to an automotive lamp.The automotive lamp is structured to be capable of controlling a lightdistribution pattern based on an image captured by a camera, and to becapable of switching multiple control modes with different combinationsof a spatial resolution of the light distribution pattern and an updatespeed of the light distribution pattern.

Another embodiment to the present invention relates to a controlapparatus for an automotive lamp or relates to the automotive lamp. Thecontrol apparatus comprises an image processing unit structured toreceive initial image data captured by a camera, to generateintermediate image data that corresponds to the initial image data, andto generate light intensity control data that determines a lightintensity distribution to be provided by the automotive lamp based onthe intermediate image data. The effective number of gradations to beused in the intermediate image data is determined for each pixel suchthat it is smaller than the number of gradations used in the initialimage data when the pixel value of the corresponding pixel of theinitial image data is within a predetermined range.

It should be noted that any combination of the components describedabove or any manifestation thereof may be mutually substituted between amethod, apparatus, system, or the like, which are also effective as anembodiment of the present invention.

With an embodiment of the present invention, such an arrangement iscapable of generating a light distribution pattern with improvedvisibility. Also, this arrangement is capable of generating a lightdistribution pattern that allows an in-vehicle camera to easilyrecognize a target. Also, with another embodiment of the presentinvention, such an arrangement is capable of generating a lightdistribution with reduced noise effects.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIG. 1 is a block diagram showing an automotive lamp according to afirst embodiment;

FIGS. 2A through 2C are diagrams for explaining the resolution of alight distribution pattern;

FIGS. 3A and 3B are diagrams for explaining generation of the lightdistribution pattern in different control modes;

FIGS. 4A and 4B are time charts showing light distribution control ofthe automotive lamp in different control modes;

FIG. 5 is a diagram for explaining multiple control modes according toan example;

FIGS. 6A and 6B are diagrams each showing a camera image divided intomultiple sub-regions;

FIG. 7A is a diagram for explaining low-contrast control, and FIG. 7B isa diagram for explaining high-contrast control;

FIG. 8 is a diagram showing an example configuration of a light sourceunit;

FIG. 9 is another example configuration of the light source unit;

FIG. 10 is a block diagram showing an automotive lamp system accordingto a second embodiment;

FIGS. 11A through 11C are diagrams for explaining the resolution of thelight distribution pattern;

FIG. 12 is a diagram for explaining signal processing for the automotivelamp shown in FIG. 10;

FIG. 13 is a diagram for explaining image processing according to afirst example;

FIG. 14A is a diagram for explaining low-contrast control, and FIG. 14Bis a diagram for explaining high-contrast control;

FIG. 15 is a diagram for explaining image processing according to asecond embodiment; and

FIGS. 16A and 16B are diagrams for explaining contrast control accordingto a third example.

DETAILED DESCRIPTION OF THE INVENTION

First, description will be made regarding the outline of an automotivelamp according to several representative embodiments.

1. An embodiment of the present invention relates to an automotive lamp.The automotive lamp is structured to be capable of controlling a lightdistribution pattern based on an image captured by a camera, and to becapable of switching multiple control modes with different combinationsof a spatial resolution of the light distribution pattern and an updatespeed of the light distribution pattern.

By performing suitable signal processing according to the drivingenvironment or the user's preference, such an arrangement is capable ofgenerating a suitable light distribution pattern.

As an embodiment, the automotive lamp may comprise: a light distributionpattern generator structured to generate a light distribution patternbased on an image captured by a camera; a light source unit structuredto emit light to a region ahead of a vehicle according to the lightdistribution pattern; and a mode controller structured to adaptivelycontrol a combination of a spatial resolution of the light distributionpattern and an update speed at which the light distribution pattern isupdated.

Also, the multiple control modes may include a first mode in which thelight distribution pattern is generated with relatively high resolutionand relatively low speed, and a second mode in which the lightdistribution pattern is generated with relatively low resolution andrelatively high speed.

This arrangement does not require a high-cost hardware component thatprovides high-speed processing. Also, the human eye has thecharacteristic of recognizing a high-speed moving object with only a lowresolution, and of recognizing a low-speed moving object with a highresolution. Accordingly, this arrangement is capable of generating alight distribution pattern that matches the characteristics of the humaneye.

Also, the control mode may be adaptively selected according to a drivingenvironment. Also, such an arrangement allows the driver to manuallyselect the control mode.

Also, the control mode may be adaptively selected according toenvironmental illumination. The human eye has characteristics thatchange according to a change between a bright environment and a darkenvironment. Accordingly, by giving consideration to the environmentalillumination, such an arrangement is capable of providing a lightdistribution pattern with improved visibility. Also, a camera involves achange of exposure time for each frame according to a change between abright environment and a dark environment under the condition in thatthe camera sensitivity is maintained at the same value. Accordingly, bygiving consideration to the environmental illumination, such anarrangement is capable of providing an operation that corresponds to theoperation of the camera.

Also, the environmental illumination may be detected based on the imagecaptured by the camera. By using the camera as an illumination sensor,this arrangement allows the number of hardware components to be reduced.

Also, the control mode may be adaptively selected according to thedriving speed. The driving speed may be used as an indicator of themoving speed of an object to be illuminated (illumination target).

Also, the control mode may be adaptively selected according to the speedof an object to be illuminated (illumination target).

Also, the control mode may be selected based on the spatial frequency ofthe image captured by the camera. The control mode may be adaptivelyselected based on the moving speed of an object included in an imagecaptured by the camera.

The control mode may be selected based on the kind of road on which theuser's vehicle is traveling.

Also, the image captured by the camera may be divided into multiplesub-regions. Also, the control mode may be set for each sub-region.Also, the image may be divided into a sub-region where it is relativelybright and a sub-region where it is relatively dark. Also, the image maybe divided into a sub-region where a target moves at a relatively highdisplacement speed and a sub-region where a target moves at a relativelylow displacement speed.

2. Another embodiment of the present invention relates to a controlapparatus for an automotive lamp. The control apparatus comprises animage processing unit structured to receive initial image data capturedby a camera, to generate intermediate image data that corresponds to theinitial image data, and to generate light intensity control data thatdetermines a light intensity distribution (light distribution pattern)to be provided by the automotive lamp based on the intermediate imagedata. The effective number of gradations to be used in the intermediateimage data is determined for each pixel such that it is smaller than thenumber of gradations used in the initial image data when a pixel valueof the corresponding pixel of the initial image data is within apredetermined range.

The light distribution pattern is handled as a set of multipleindividual regions (meshes). The light intensity of each mesh isdetermined based on the pixel value of the pixel at the correspondingposition included in the initial image data. With this arrangement,noise is superimposed on each pixel value. In a case in which noise isincluded in a particular pixel value range, in some cases, noise effectsare noticeable in the light distribution pattern. In order to solve sucha problem, when a pixel included in the initial image data has asignificant noise effect on the final light intensity distribution, theeffective number of gradations is reduced for the pixel. Thisarrangement is capable of generating a light distribution with reducednoise effects due to a camera. By reducing the number of gradations foronly a predetermined range, this arrangement maintains the original highnumber of gradations for the pixels where noise is not noticeable.

The predetermined range may be a range from zero up to a predeterminedupper limit value. Also, the predetermined range may be a range from apredetermined lower limit value up to the maximum gradation value. Also,multiple predetermined ranges may be employed.

Also, processing for generating the light intensity control data mayinclude comparing a pixel value of the intermediate image data or imagedata generated based on the intermediate image data with a thresholdvalue. In this case, by determining the predetermined range according tothe threshold value, this arrangement is capable of reducing noiseeffects.

Also, processing for generating the light intensity control data mayinclude changing the contrast of the intermediate image data or imagedata generated based on the intermediate image data. In a case in whichthe contrast is lowered (or raised), in some cases, noise in a darkportion is amplified. In order to solve such a problem, by reducing thenumber of gradations for a predetermined range that corresponds to adark portion, this arrangement allows the noise effects to be reduced.

Also, processing for generating the light intensity control data mayinclude gradation inversion of the pixel values of the intermediateimage data or image data generated based on the intermediate image data.In this case, as the intermediate image data becomes dark, the lightintensity is raised. Accordingly, the noise included in a dark portionis emphasized in a bright region in the light intensity distribution. Inorder to solve such a problem, by reducing the number of gradations ofthe predetermined range that corresponds to such a dark portion, thisarrangement allows the noise effects to be reduced.

The image processing unit may compare each pixel value of theintermediate image data with a threshold value, and may generate thelight intensity control data based on the comparison result. Directingattention to multiple adjacent pixels, in a case in which a given pixelvalue exceeds the threshold value and another pixel value does notexceed the threshold value, the noise effects on the light intensitycontrol data become noticeable. In this case, by reducing the number ofgradations of the intermediate image data, this arrangement allows thenoise effects to be reduced.

Also, processing for generating the intermediate image data may includemultiplying each pixel value of the initial image data by a coefficientthat is smaller than 1.

Also, processing for generating the intermediate image data may includerounding lower N bits (N represents an integer of 1 or more) of thepixel values of the initial image data.

Also, the image processing unit may change the degree of reducing thenumber of gradations according to the amplitude of noise included in theinitial image data. In some cases, the amount of noise changes dependingon the temperature and the environment. This arrangement allows thenoise effects to be appropriately reduced according to the situation.

The above is the outline of the automotive lamp. Description will bemade below with reference to the drawings regarding the presentinvention based on preferred embodiments. The embodiments have beendescribed for exemplary purposes only, and are by no means intended torestrict the present invention. Also, it is not necessarily essentialfor the present invention that all the features or a combination thereofbe provided as described in the embodiments. The same or similarcomponents, members, and processes are denoted by the same referencenumerals, and redundant description thereof will be omitted asappropriate.

The scale and the form of each portion in the drawings are determinedfor convenience for ease of description, and are by no means intended tobe restricted in particular in the absence of explicit definition. In acase in which terms such as “the first”, “the second”, or the like areemployed in the present specification and claims, such terms are by nomeans to indicate order or importance. Rather, such terms are used todistinguish a given component from another component.

FIG. 1 is a block diagram showing an automotive lamp system according toa first embodiment. An automotive lamp system 100 includes an automotivelamp 200, an in-vehicle ECU (Electronic Control Unit) 102, and a battery104. The battery voltage V_(BAT) generated by the battery 104 issupplied to the automotive lamp 200 as a power supply voltage. Thein-vehicle ECU 102 and the automotive lamp 200 are each configured toconform to a protocol such as CAN (Controller Area Network), LIN (LocalInternet Network), or the like, which allows these devices tocommunicate with each other. The in-vehicle ECU 102 controls the on/offstate of the automotive lamp 200. Furthermore, the in-vehicle ECU 102transmits vehicle information such as vehicle speed information,steering information, etc., to the automotive lamp 200. Furthermore,this arrangement allows the automotive lamp 200 to transmit a failsignal or the like to the in-vehicle ECU 102.

The automotive lamp 200 is configured to dynamically and adaptivelycontrol a light distribution pattern PTN based on an image (which willalso be referred to as a “camera image IMG” hereafter) captured by acamera unit 210. It should be noted that the camera image IMGcorresponds to a single piece of frame data that forms a moving image.The camera unit 210 may include only a single camera. Also, the cameraunit 210 may include multiple cameras configured to provide differentresolutions and/or different frame rates. In a case in which the cameraunit 210 includes multiple cameras, the camera image IMG collectivelyrepresents the output data of the multiple cameras.

The light distribution pattern PTN represents a two-dimensional lightintensity distribution having an illumination pattern 902 formed by theautomotive lamp 200 on a virtual vertical screen 900 ahead of the user'svehicle. The automotive lamp 200 is capable of adaptively switching thecontrol mode between the multiple control modes for generating the lightdistribution pattern PTN. There is a difference in a combination of thespatial resolution of the light distribution pattern PTN and the updatespeed (switching speed) thereof between the multiple control modes.

The light distribution pattern PTN is divided into multiple meshes(regions). Each mesh is provided with a uniform light intensity. Thespatial resolution of the light distribution pattern PTN corresponds tothe fineness (roughness) of the meshes.

FIGS. 2A through 2C are diagrams for explaining the resolution of thelight distribution pattern PTN. FIG. 2A shows an example of the cameraimage IMG. FIGS. 2B and 2C are diagrams each showing an example of thelight distribution pattern PTN that corresponds to the camera image IMGshown in FIG. 2A. Here, for ease of description, description will bemade regarding an example in which a predetermined target is extractedfrom the camera image IMG, and a particular mesh where the predeterminedtarget exists is shielded (i.e., with a light intensity of zero). Such apredetermined target is a target to which glare is not to be imparted.Examples of such a predetermined target include a leading vehicle 904,an oncoming vehicle 906, and a pedestrian 908. In FIGS. 2B and 2C, theregion to be shielded is hatched. FIG. 2B shows a light distributionpattern PTN having a resolution that is higher than that shown in FIG.2C. In a case in which the light distribution pattern is generated withhigher resolution, this arrangement is capable of providinghigher-precision shielding according to the shape of the predeterminedtarget.

In a case of further raising the resolution of the light distributionpattern PTN, this arrangement allows only a rear window portion of theleading vehicle 904 or only a front window portion of the oncomingvehicle 906 to be shielded while proactively raising the light intensityfor the vehicle body. Similarly, such an arrangement allows only theface portion of the pedestrian 908 to be shielded while proactivelyraising the light intensity for the body portion. This allows thedriver's visibility to be further improved while preventing theoccurrence of glare.

Returning to FIG. 1, description will be made regarding a specificconfiguration of the automotive lamp 200. The automotive lamp 200includes a control unit 220 and a light source unit 230 in addition tothe camera unit 210. It should be noted that FIG. 1 shows an arrangementin which the camera unit 210 is built into the automotive lamp 200.Also, the camera unit 210 may be provided on the vehicle side.

The control unit 220 includes a light distribution pattern generator 222and a mode controller 224. The control unit 220 is also referred to as a“lighting device ECU”. The light distribution pattern generator 222generates a light distribution pattern PTN based on the camera imageIMG. The control unit 220 can be configured as a digital processor. Forexample, the control unit 220 may be configured as a combination of aCPU or a microcontroller and a software program. Also, the control unit220 may be configured as an FPGA (Field Programmable Array), ASIC(Application Specified IC), or the like.

The light source unit 230 is configured to receive data for indicatingthe light distribution pattern PTN from the light distribution patterngenerator 222, and to form a light intensity distribution in a regionahead of the vehicle according to the light distribution pattern PTN.The configuration of the light source unit 230 is not restricted inparticular. For example, the light source unit 230 may include asemiconductor light source such as an LD (laser diode), LED(light-emitting diode), or the like, and a lighting circuit that drivesthe semiconductor light source so as to turn on the semiconductor lightsource. In order to form the light intensity distribution thatcorresponds to the light distribution pattern PTN, the light source unit230 may include a matrix pattern forming device such as a DMD (DigitalMirror Device), liquid crystal device, or the like.

The mode controller 224 adaptively controls a combination of the spatialresolution of the light distribution pattern PTN and the update speed(frame rate) of the light distribution pattern PTN, i.e., the controlmode for the light distribution generator 222.

The above is the basic configuration of the automotive lamp 200. Next,description will be made regarding the operation thereof.

FIGS. 3A and 3B are diagrams for explaining the formation of the lightdistribution pattern PTN in different control modes. FIG. 3A shows acontrol mode with the distribution pattern PTN update period Ts₁ that isshorter than the update period Ts₂ employed in the control mode shown inFIG. 3B. Furthermore, the control mode shown in FIG. 3A provides thelight distribution pattern PTN with a resolution that is lower than thatprovided by the control mode shown in FIG. 3B.

FIGS. 4A and 4B are time charts showing the light distribution controlof the automotive lamp 200 in different control modes. FIG. 4A shows acontrol mode designed prioritizing the resolution. The camera image IMGis generated for every predetermined frame period T_(F). The controlunit 220 receives the camera image IMG for every predetermined number offrames, and generates the light distribution pattern PTN by imageprocessing based on the camera image IMG thus received. The processingtime T_(P), which is a period of time required to generate a singlehigh-resolution light distribution pattern PTN based on a single cameraimage IMG, is longer than the frame period T_(F). Accordingly, theupdate period T_(S) of the light distribution pattern PTN is restrictedby the processing time T_(P).

FIG. 4B shows a control mode designed prioritizing the update speed. Thecontrol unit 220 receives the camera image IMG for every frame, andgenerates the light distribution pattern PTN by image processing basedon the camera image IMG thus received. The processing time T_(P), whichis a period of time required to generate a single low-resolution lightdistribution pattern PTN based on a single camera image IMG, is shorterthan the frame period T_(F).

FIG. 5 is a diagram for explaining the multiple control modes accordingto an example. The horizontal axis represents the update speed (thereciprocal of the update period), and the vertical axis represents theresolution. The light distribution pattern generator 222 is configuredto be switched between at least a first mode MODE1, and a second modeMODE2. In the first mode MODE1, the light distribution generator 222generates the light distribution pattern PTN with a relatively highresolution and low speed. In the second mode MODE2, the lightdistribution generator 222 generates the light distribution pattern PTNwith a relatively low resolution and high speed.

As described above, the control unit 220 may be configured as aprocessor such as a microcontroller, CPU, or the like. The calculationamount required for the light distribution pattern generator 222 risesaccording to an increase in the resolution of the light distributionpattern PTN, and according to the update speed of the light distributionpattern PTN.

In FIG. 5, in order to generate the light distribution pattern PTN in aregion 910 that corresponds to the highest resolution and the highestupdate speed, the processor is required to have very high calculationpower. However, typically, such a high-speed processor has a problem ofa high cost. In many cases, it is difficult to mount such a high-speedprocessor on the automotive lamp from the cost viewpoint. In otherwords, it can be said that, in a case in which the processor does nothave such high calculation power, there is a tradeoff relation betweenthe resolution and the update speed. In a case in which there is such ahardware restriction, the operation region of the light distributionpattern generator 222 may preferably be restricted to a region 912 shownin FIG. 5. This allows the calculation power required for the processorto be reduced. Such an arrangement does not require such a high-cost CPUor the like. That is to say, this arrangement allows a low-costprocessor to be employed.

A third mode MODE3 may be supported as an intermediate mode of the firstmode MODE1 and the second mode MODE2 in addition to the first mode MODE1and the second mode MODE2 for operating in a sub-region within theregion 912. Furthermore, a fourth mode MODE4 may be supported as acombination of a low resolution mode and a low update speed mode.

By supporting the first mode MODE1 and the second mode MODE2, such anarrangement provides the following effect. The human eye is capable ofrecognizing a high-speed object with only a low resolution. In contrast,the human eye is capable of recognizing a low-speed object with highresolution. Accordingly, by configuring the control mode to be switchedbetween the first mode MODE1 and the second mode MODE2, this arrangementis capable of generating a light distribution pattern that matches thephysiological characteristics of the human eye.

Next, description will be made regarding the switching of the controlmode. Preferably, the control mode is adaptively selected according tothe driving environment. Specifically, the control mode can be selectedbased on at least one from among the following three parameters.Alternatively, the control mode may be selected giving consideration tothe multiple parameters.

1. Ambient Brightness (Environmental Illumination).

As the first parameter, the ambient brightness is employed. There is alarge difference in the ambient brightness even in an environment inwhich a headlight is to be turned on. For example, it is brighter inearly evening or early morning than at night. Also, it is brighter in anurban area where there are many streetlights than in a suburban areawhere there are few streetlights even at the same time of night. Also,there is a large difference in brightness between tunnel interiorsdepending on the number of illumination devices or the luminanceprovided by each illumination device.

The human eye includes rod cells having low resolution and highsensitivity and cone cells having high resolution and low sensitivity.It is known that, in a bright environment, the cone cells are activated.Conversely, in a dark environment, the rod cells are activated. That isto say, the human eye has low resolution in a dark environment.Accordingly, it can be same that, in a case in which the lightdistribution pattern PTN is controlled with high resolution in such adark environment, the human eye is not able to recognize the lightdistribution pattern PTN with such a high resolution.

Accordingly, the mode controller 224 may select the control modeaccording to the ambient brightness. Specifically, as it becomes bright,the mode controller 224 may select a higher-resolution control mode.Conversely, as it becomes dark, the mode controller 224 may select alower-resolution control mode. In a case in which the first mode MODE1through the third mode MODE3 shown in FIG. 5 are selectable, when thesurroundings are bright, the mode controller 224 may select the firstmode MODE1. As it becomes dark, the mode controller 224 may select thethird mode MODE3 and the second mode MODE2 in this order.

In order to measure the ambient brightness, as shown in FIG. 1, theautomotive lamp 200 may be provided with an illumination sensor 240 thatmeasures the environmental illumination. The mode controller 224 mayselect a control mode having a suitable resolution according to theenvironmental illumination.

Instead of the illumination sensor 240, the camera unit 210 may be usedas an illumination sensor. The camera image IMG includes informationwith respect to the environmental illumination. Accordingly, the modecontroller 224 may estimate the environmental illumination by subjectingthe camera image IMG to calculation processing. For example, the averageof values of multiple pixels (pixel values) of the camera image IMG maybe calculated so as to estimate the environmental illumination. Also,the pixel values may be extracted from a region of the camera image IMGthat is not illuminated by output light emitted from the automotive lamp200, and the environmental illumination may be estimated based on thepixel values thus extracted. By estimating the environmentalillumination based on the camera image IMG, this arrangement allows theillumination sensor to be omitted.

2. Relative Speed of an Illumination Target With Respect to the User'sVehicle

As a second parameter, the relative speed of an illumination target(target) with respect to the user's vehicle is employed. Examples ofsuch an illumination target as used here include a vehicle, road sign,pedestrian, road surface, delineator, streetlight, etc. In other words,the control mode may be selected according to the time frequency of theview ahead of the user's vehicle. That is to say, in a case in which theillumination target moves at a relatively high speed with respect to theuser's vehicle, a control mode with a high update speed may be selected.Also, the control mode may be selected such that its update speedbecomes low according to a reduction in the relative speed. In a case inwhich the first mode MODE1 through the third mode MODE3 shown in FIG. 5are selectable, in a situation in which the relative speed is high, thesecond mode MODE2 may be selected. Also, the third mode MODE3 and thefirst mode MODE1 may be selected in this order according to a reductionin the relative speed.

For example, the mode controller 224 may switch the control mode basedon the displacement speed of the illumination target included in thecamera image IMG. This enables control giving consideration to therelative speed of the illumination target with respect to the user'svehicle.

Also, in many cases, when the user's vehicle is driven at a high speed,the relative speed tends to increase. Also, in many cases, when theuser's vehicle is driven at low speed, the relative speed tends todecrease. Accordingly, the light distribution pattern generator 222 mayswitch the control mode based on the user's vehicle driving speed.

3. Shape and Configuration of Illumination Target

As a third parameter, the spatial resolution of the shape andconfiguration of the illumination target (or target) is employed. Inother words, the third parameter is the spatial resolution of the viewahead of the vehicle. When the view has a high spatial frequency, acontrol mode with a high resolution may be selected. As the spatialfrequency becomes lower, a control mode with a low resolution may beselected. In a case in which the first mode MODE1 through the third modeMODE3 shown in FIG. 5 are selectable, in a situation in which thespatial frequency is high, the first mode MODE1 may be selected. As thespatial frequency becomes lower, the third mode MODE3 and the secondmode MODE2 may be selected in this order.

The spatial frequency of the view ahead of the vehicle may be calculatedbased on the camera image IMG. The mode controller 224 may subject theimage data to Fourier transformation so as to calculate the spatialfrequency.

The mode controller 224 may directly or indirectly acquire each of thefirst parameter through the third parameter so as to select the controlmode. Also, the first parameter through the third parameter may beestimated based on the driving environment. Accordingly, the modecontroller 224 may select the control mode based on the drivingenvironment.

With an example, the control mode may be selected according to the kindof the road on which the user's vehicle is traveling. The kinds of roadscan be classified into urban areas, suburban areas, expressways,tunnels, etc. The kind of road may be judged based on informationreceived from a car navigation system, based on information with respectto the user's vehicle such as vehicle speed information, steeringinformation, etc., or based on an image captured by the camera unit 210.

Directing attention to the first parameter, it is relatively bright inan urban area and the user is able to recognize an object with highresolution. Accordingly, the first mode MODE1 or the third mode MODE3may be selected. Conversely, it is relatively dark in a suburban areaand the human eye is only able to recognize an object with lowresolution. Accordingly, the second mode MODE2 or the third mode MODE3may be selected.

Directing attention to the second parameter, in many cases, thetraveling speed of the vehicle is low in an urban area, which tends toreduce the relative speed of the illumination target with respect to theuser's vehicle. Accordingly, in this case, the first mode MODE1 or thethird mode MODE3 may be selected. Conversely, the traveling speed of thevehicle increases on an expressway or in a suburban area, which tends toincrease the relative speed of the illumination target with respect tothe user's vehicle. Accordingly, in this case, the second mode MODE2 orthe third mode MODE3 may be selected.

Directing attention to the third parameter, in an urban area, there arerelatively many small-size targets such as pedestrians, road signs, orthe like. Accordingly, the spatial frequency tends to be high in such anurban area. Accordingly, in this case, the first mode MODE1 or the thirdmode MODE3 may be selected. On the other hand, on an expressway or in asuburban area, there are a relatively small number of pedestrians orroad signs. Accordingly, the spatial frequency tends to be low. In thiscase, the second mode MODE2 or the third mode MODE3 may be selected.

Description has been made above regarding an example in which a singlelight distribution pattern is generated in a single control mode.However, the present invention is not restricted to such an example.Also, the single camera image IMG may be divided into multiplesub-regions. Also, an optimum control mode may be selected for eachsub-region.

FIGS. 6A and 6B are diagrams each showing the camera image IMG dividedinto multiple sub-regions. FIG. 6A shows an example in which the cameraimage IMG is divided into two sub-regions, i.e., an upper region and alower region. FIG. 6B shows an example in which the camera image IMG isdivided into five sub-regions, i.e., a central region, upper region,lower region, left region, and right region.

There is a large difference between sub-regions in the tendencies of thebrightness of the view ahead of the user's vehicle (first parameter),the time frequency (second parameter), and the spatial frequency (thirdparameter). Accordingly, by dividing the camera image IMG into multiplesub-regions, such an arrangement is capable of providing more suitablecontrol.

In the dividing pattern shown in FIG. 6A, the upper sub-region SR₁ caninclude an illumination target at a longer distance than that in thelower sub-region SR₂. Accordingly, in many cases, in the uppersub-region SR₁, the displacement speed is low, i.e., the time frequencyis low. Furthermore, an object at a long distance appears small ascompared with an object at a short distance. Accordingly, in the uppersub-region SR₁, in many cases, the spatial frequency is high.Accordingly, in the upper sub-region SR₁, a mode prioritizing theresolution may be used. In contrast, in the lower sub-region SR₂, a modeprioritizing the update speed may be used.

In the dividing pattern shown in FIG. 6B, the central sub-region SR₁includes a vanishing point. Accordingly, the central sub-region SR₁ caninclude an illumination target at a longer distance than those in theother sub-regions SR₂ through SR5, leading to a low displacement speed.That is to say, in the central sub-region SR₁, in many cases, the timefrequency is low, and the spatial frequency is high. Accordingly, inthis case, in the sub-region SR₁, a mode prioritizing the resolution maybe used.

In contrast, in the left and right sub-regions SR₂ and SR₃, there is ahigh possibility of the appearance of an oncoming vehicle or a vehicleovertaking the user's vehicle. In many cases, such a target moves at ahigh displacement speed. Accordingly, in the sub-region SR₂ or SR3, amode prioritizing the update speed may be used.

It should be noted that the dividing pattern may be adaptively switchedaccording to the kind of road on which the vehicle is traveling, theuser's vehicle speed, or the like.

Next, description will be made regarding image processing in the lightdistribution pattern generator 222.

As a simplest example, the light distribution pattern generator 222 maydetect a particular target based on the camera image IMG, and mayperform control so as to shield a portion that corresponds to the targetthus detected.

As an advanced example, the light distribution pattern generator 222 maychange the light intensity for each mesh of the light distributionpattern PTN based on the value of the corresponding pixel (pixel value)that corresponds to the mesh. Such control will be referred to as“contrast control”. FIGS. 6A and 6B are diagrams for explaining thecontrast control. The horizontal axis represents the pixel value of thecamera image. The vertical axis represents the corresponding lightintensity for the mesh.

FIG. 7A is a diagram for explaining low-contrast control. In thelow-contrast control, the light intensity is set according to thebrightness of the illumination target, i.e., according to the pixelvalue. Specifically, the light intensity is reduced according to anincrease in the brightness of an object, and is raised according to areduction in the brightness thereof. This reduces a difference inbrightness between a dark portion and a bright portion. In particular,this raises the visibility for a dark portion. It should be noted that,in addition to the low-contrast control based on a monotonicallydecreasing linear function as indicated by the solid line, thelow-contrast control may be provided in a discrete manner based on amonotonically decreasing stepwise function as indicated by the brokenline. Also, the low-contrast control may be provided based on anonlinear function as indicated by the curve of alternately long andshort dashes. Alternatively, the light intensity for each mesh may becontrolled by feedback control such that the pixel value thereofapproaches a predetermined target value.

FIG. 7B is a diagram for explaining high-contrast control. In thehigh-contrast control, the light intensity is set according to thebrightness of the illumination target, and specifically, is raisedaccording to an increase in the brightness of an object, and is reducedaccording to a reduction in the brightness thereof. This increases adifference in brightness between a dark portion and a bright portion.The view having such a large brightness difference provides an advantagein that the human eye can easily recognize the position and the shape ofan object instantaneously. In addition to the high-contrast controlbased on a monotonically increasing linear function, the high-contrastcontrol may be provided based on a monotonically increasing stepwisefunction as indicated by the broken line. Also, the high-contrastcontrol may be provided based on a nonlinear function as indicated bythe curve of alternately long and short dashes.

Next, description will be made regarding an example configuration of thelight source unit 230. FIG. 8 is a diagram showing an exampleconfiguration of the light source unit 230. A light source unit 230Ashown in FIG. 8 includes a light source 232, a lighting circuit 234, anda patterning device 236. In addition, the light source unit 230A mayinclude an unshown reflection optical system or transmission opticalsystem.

As the light source 232, a high-luminance semiconductor light sourcesuch as an LED or LD may preferably be employed. The lighting circuit234 supplies a stabilized driving current (lamp current) to the lightsource 232 such that the light source 232 emits light with apredetermined luminance. The output light emitted from the light source232 is input to the patterning device 236.

As the patterning device 236, a DMD or a liquid crystal panel may beemployed. The DMD is configured as an array of micromirror devices eachhaving a reflection angle that can be controlled independently.Specifically, the DMD is configured such that the effective reflectancecan be controlled for each micromirror device in a multiple gradations.On the other hand, the liquid crystal panel is configured as an array ofpixels each having a transmissivity that can be controlledindependently. Specifically, the liquid crystal panel is configured suchthat the transmissivity can be controlled for each pixel in a multiplegradations.

FIG. 9 is a diagram showing another example configuration of the lightsource unit 230. A light source unit 230B shown in FIG. 9B is configuredas a scanning lighting device including a light source 232, a lightingcircuit 234, and a scanning optical system 238. The scanning opticalsystem 238 is configured to be capable of scanning an output beamemitted from the light source 232. For example, the scanning opticalsystem 238 may include a motor 239 a and a reflector (blade) 239 battached to a rotational shaft of the motor 239 a. When the motor 239 ais rotated, the angle defined by the reflection face of the reflector239 b and the output beam changes, thereby scanning the scanning beamBM_(SCAN). A projector optical system 235 configured as a transmissionoptical system or a reflection optical system may be arranged on anoptical path of the scanning beam BM_(SCAN).

Description has been made above regarding an aspect of the presentinvention based on the first embodiment. Next, description will be maderegarding modifications relating to the first embodiment.

Modification 1

Description has been made in the embodiment regarding an arrangement inwhich the control mode is adaptively switched by the mode controller224. Also, an arrangement may be made configured to allow the driver tomanually select the control mode. There are differences in thecharacteristics of the cells of the human eye between individuals. Also,there are also differences in the user's desired light distributionpattern between individuals. Accordingly, by providing the driver withthe freedom to select the control mode, such an arrangement enables therealization of light distribution patterns suitable for individualdrivers.

Modification 2

Also, an arrangement may be made configured to allow the driver to inputa parameter to be referenced when the control mode is to beautomatically controlled. This allows the control mode to be switched toa suitable control mode for each driver.

Modification 3

Description has been made in the embodiment regarding an arrangementconfigured giving consideration to the limitations of the processingspeed supported by the hardware component of the control unit 220.However, the present invention is not restricted to such an arrangement.Also, the control unit 220 may be configured to operate in the range 910that corresponds to the maximum resolution and the maximum update speedshown in FIG. 5. This arrangement also provides the advantage of thepresent invention.

Modification 4

Description has been made in the embodiment regarding processing mainlywith a principal objective of providing improved driver visibility.However, the present invention is not restricted to such an arrangement.It is important for automated driving or semi-automated driving todetect a target by means of an in-vehicle camera. Accordingly, thecontrol mode may be adaptively switched so as to allow the in-vehiclecamera to easily recognize a target.

Second Embodiment

FIG. 10 is a block diagram showing an automotive lamp system accordingto a second embodiment. An automotive lamp system 100 includes anautomotive lamp 200, an in-vehicle ECU (Electronic Control Unit) 102,and a battery 104. The battery voltage V_(BAT) generated by the battery104 is supplied to the in-vehicle lighting deice 200 as a power supplyvoltage. The in-vehicle ECU 102 and the automotive lamp 200 are eachconfigured to conform to a protocol such as CAN (Controller AreaNetwork), LIN (Local Internet Network), or the like, which allows thesedevices to communicate with each other. The in-vehicle ECU 102 controlsthe on/off state of the automotive lamp 200. Furthermore, the in-vehicleECU 102 transmits vehicle information such as vehicle speed information,steering information, etc., to the automotive lamp 200. Furthermore,this arrangement allows the automotive lamp 200 to transmit a failsignal or the like to the in-vehicle ECU 102.

The automotive lamp 200 is configured to dynamically and adaptivelycontrol a light distribution pattern PTN based on an image (which willalso be referred to as “initial image data IMG₁” hereafter) captured bya camera unit 210. It should be noted that the initial image data IMG₁corresponds to a single piece of frame data that forms a moving image.The camera unit 210 may include only a single camera. Also, the cameraunit 210 may include multiple cameras configured with differentresolutions and/or different frame rates. In a case in which the cameraunit 210 includes multiple cameras, the initial image data IMG₁collectively represents the output data of the multiple cameras.

The light distribution pattern PTN represents a two-dimensional lightintensity distribution having an illumination pattern 902 formed by theautomotive lamp 200 on a virtual vertical screen 900 ahead of the user'svehicle. In order to generate the light distribution pattern PTN, theautomotive lamp 200 includes a control unit (control apparatus) 220 anda light source unit 230. The control unit 220 is also referred to as a“lighting device ECU”).

The light distribution pattern PTN is divided into multiple meshes(individual regions). Each mesh is provided with a uniform lightintensity. The spatial resolution of the light distribution pattern PTNcorresponds to the fineness (roughness) of the meshes. As the resolutionof the light distribution pattern, one from among WUXGA (1920×1200), FHD(1920×1080), FWXGA (1366×768 or 1280×720), SXGA (1280×1024), WXGA(1280×800), WVGA (800×480), VGA (640×480), and QVGA (320×240) may beemployed. However, the present invention is not restricted to such anexample. Also, the resolution that can be employed may be furtherreduced. Also, as the resolution that can be employed, a finerresolution that corresponds to 4K or 8K may be employed.

FIGS. 11A through 11C are diagrams for explaining the light distributionpattern PTN. FIG. 11A shows an example of the initial image data IMG₁.FIGS. 11B and 11C are diagrams each showing an example of the lightdistribution pattern PTN that corresponds to the initial image data IMG₁shown in FIG. 11A. Here, for ease of description, description will bemade regarding an example in which a predetermined target is extractedfrom the initial image data IMG₁, and a particular mesh where thepredetermined target exists is shielded (i.e., with the light intensityof zero). Such a predetermined target is a target to which glare is notto be imparted. Examples of such a predetermined target include aleading vehicle 904, an oncoming vehicle 906, and a pedestrian 908. InFIGS. 11B and 11C, the region to be shielded is hatched. FIG. 11B showsa light distribution pattern PTN having a resolution that is higher thanthat shown in FIG. 11C. In a case in which the light distributionpattern is generated with higher resolution, this arrangement is capableof providing higher-precision shielding according to the shape of thepredetermined target.

In a case of further raising the resolution of the light distributionpattern PTN, this arrangement allows only a rear window portion of theleading vehicle 904 or only a front window portion of the oncomingvehicle 906 to be shielded while proactively raising the light intensityfor the vehicle body. Similarly, such an arrangement allows only theface portion of the pedestrian 908 to be shielded while proactivelyraising the light intensity for the body portion. This allows thedriver's visibility to be further improved while preventing theoccurrence of glare.

Returning to FIG. 10, description will be made regarding a specificconfiguration of the automotive lamp 200. The automotive lamp 200includes a control unit 220 and a light source unit 230 in addition tothe camera unit 210. It should be noted that FIG. 10 shows anarrangement in which the camera unit 210 is built into the automotivelamp 200. Also, the camera unit 210 may be provided on the vehicle side.

The control unit 220 integrally controls the automotive lamp 200. Thecontrol unit 220 includes an image processing unit 221 and an unshowndifferent processing unit. The image processing unit 221 may beconfigured as a digital processor. For example, the image processingunit 221 may be configured as a combination of a CPU or amicrocontroller and a software program. Also, the image processing unit221 may be configured as an FPGA (Field Programmable Gate Array), ASIC(Application Specified IC), or the like.

A preprocessing unit 226 receives the initial image data IMG₁ capturedby the camera unit 210, and generates intermediate image data IMG₂ thatcorresponds to the initial image data IMG₁.

The effective number of gradations to be used in the intermediate imagedata IMG₂ is determined for each pixel such that it is smaller than thenumber of gradations employed in the initial image data IMG₁ when thepixel value of the corresponding pixel of the initial image data IMG₁ isincluded within the predetermined range RNG. For ease of understanding,description will be made in the present embodiment regarding anarrangement in which such image data is configured as a monochromeimage. Also, such image data may be configured as a color image. Whenthe intermediate image data IMG₂ is to be generated based on the initialimage data IMG₁, the preprocessing unit 226 may perform image processingfor reducing the resolution.

The light distribution pattern generator 222 generates light intensitycontrol data that defines a light intensity distribution (lightdistribution pattern PTN) of the automotive lamp 200 based on theintermediate image data IMG₂. The generating method for the lightdistribution pattern PTN based on the intermediate image data IMG₂ isnot restricted in particular. The light intensity provided to individualregions (meshes) included in the light distribution pattern PTN isdetermined based on the values (pixel values) of the correspondingpixels of the intermediate image data IMG₂.

The light source unit 230 is configured to receive the light intensitycontrol data for indicating the light distribution pattern PTN from thelight distribution pattern generator 222, and to form a light intensitydistribution in a region ahead of the vehicle according to the lightdistribution pattern PTN. The configuration of the light source unit 230is not restricted in particular. For example, the light source unit 230may include a semiconductor light source such as an LD (laser diode),LED (light-emitting diode), or the like, and a lighting circuit thatdrives the semiconductor light source so as to turn on the semiconductorlight source. In order to form the light intensity distribution thatcorresponds to the light distribution pattern PTN, the light source unit230 may include a matrix pattern forming device such as a DMD (DigitalMirror Device), liquid crystal device, or the like.

The above is the configuration of the automotive lamp 200. Next,description will be made regarding the operation thereof. FIG. 12 is adiagram for explaining the signal processing for the automotive lamp 200shown in FIG. 10. For simplification of description, FIG. 12 shows asimple example in which image data is configured as one-dimensionalimage data. The predetermined range RNG to be subjected to processingfor reducing the number of gradations is hatched. In this example,twelve gradations, i.e., the pixel values 0 through 11, are employed asthe predetermined range RNG. Referring to the intermediate image dataIMG₂, the effective number of gradations of the predetermined range RNGis reduced to 3.

The initial image data IMG₁, which is original image data, includesnoise N in the form of random noise. From among the noise, the noiseincluded in the predetermined range RNG can be removed by reducing thenumber of gradations.

It should be noted that as the processing for reducing the number ofgradations, several lower bits may be rounded (rounding-up orrounding-down processing). In the example shown in FIG. 12, the lowertwo bits are set to zero as the rounding processing. The number of lowerbits to be rounded, i.e., the degree of reducing the number ofgradations, may preferably be determined giving consideration to theamplitude of the noise N and the effects of the noise N on the lightdistribution pattern generated in a final stage. Accordingly, the imageprocessing unit 221 may change the degree of reducing the number ofgradations according to the amplitude of noise included in the initialimage data IMG₁ (i.e., S/N ratio).

The above is the operation of the automotive lamp 200. With theautomotive lamp 200, from among the pixels included in the initial imagedata IMG₁, for pixels where there is a noticeable noise effect on thefinal light intensity distribution, the effective number of gradationsis reduced for such pixels. Such an arrangement is capable of forming alight distribution with reduced noise effects due to the camera.Furthermore, by reducing the number of gradations for only the hatchedpredetermined range RNG, this arrangement allows the original highnumber of gradations to be maintained for the other ranges where noiseis not noticeable.

The present invention encompasses various kinds of apparatuses,circuits, and methods that can be regarded as a block configuration or acircuit configuration shown in FIG. 10, or that can be derived from theaforementioned description. That is to say, the present invention is notrestricted to a specific configuration. More specific description willbe made below regarding an example configuration for clarification andease of understanding of the essence of the present invention and thecircuit operation. That is to say, the following description will by nomeans be intended to restrict the technical scope of the presentinvention.

Detailed description will be made with reference to several examplesregarding the relation between image processing supported by the lightdistribution pattern generator 222 and generation of the intermediateimage data.

FIRST EXAMPLE

FIG. 13 is a diagram for explaining image processing according to afirst example. As a simplest example, the light distribution patterngenerator 222 may perform control in which a predetermined target isdetected based on the initial image data IMG₁, and a portion thatcorresponds to the target thus detected is shielded (or the lightintensity is reduced). Examples of an object to be shielded include anoncoming vehicle, leading vehicle, light-emitting object such as astreetlight, electronic bulletin board, or the like, etc. The oncomingvehicle and the leading vehicle are required to be shielded from theviewpoint of suppressing the occurrence of glare. Also, it ismeaningless to emit light from a headlamp to a light-emitting objectsuch as a streetlight, electronic bulletin board, or the like.

Accordingly, the image processing unit 221 may perform control suchthat, when a pixel value of the initial image data IMG₁ exceeds apredetermined threshold value TH, the image processing unit 221 mayjudge that there is a high probability of the existence of alight-emitting object in a given region, and may perform control so asto shield the given region (or may reduce the light intensity for thegiven region).

In a case of providing such control, when a pixel value of the initialimage data IMG₁ is in the vicinity of the threshold value TH, the pixelvalue on which noise has been superimposed crosses the threshold valueTH. In this case, an undesired shielded region is formed according torandom noise. This situation is shown as the light distribution patternin the third graph from the top in FIG. 13.

In order to solve such a problem, the predetermined range RNG and thenumber of gradations of the intermediate image data to be set for thepredetermined range RNG are determined according to the noise amplitudeand the threshold value TH. This arrangement allows the noise effects tobe reduced. This effect is shown as the light distribution pattern inthe fourth graph from the top in FIG. 13.

SECOND EXAMPLE

The light distribution pattern generator 222 reduces the contrast of theview ahead of the vehicle based on the initial image data IMG₁. Also,the light distribution pattern generator 222 may support an operationfor raising the contrast. The “contrast” as used here represents thebrightness ratio between a dark portion and a bright portion.

More specifically, in order to reduce the contrast, the light intensitymay preferably be raised for a dark portion (low-reflectance portion).Conversely, the light intensity may preferably be lowered for a brightportion. In other words, the light intensity may preferably be adjustedaccording to the brightness of the illumination target. Specifically,the light intensity may preferably be lowered according to an increasein the brightness of an object, i.e., may preferably be raised accordingto a reduction in the brightness thereof. That is to say, eachindividual region of the light distribution pattern may preferably beadjusted such that the light intensity is raised according to areduction in the pixel value of the corresponding pixel of the initialimage data IMG₁, i.e., is lowered according to an increase in the pixelvalue. In the present specification, this processing will be referred toas “low-contrast control”.

FIG. 14A is a diagram for explaining the low-contrast control. Thisreduces the brightness difference between a dark portion and a brightportion. Accordingly, in particular, this allows the visibility to beimproved for a dark portion. It should be noted that, in addition to thelow-contrast control based on a monotonically decreasing linear functionas indicated by the solid line, the low-contrast control may be providedin a discrete manner based on a monotonically decreasing stepwisefunction as indicated by the broken line. Also, the low-contrast controlmay be provided based on a nonlinear function as indicated by the curveof alternately long and short dashes. Alternatively, the light intensityfor each mesh may be controlled by feedback control such that the pixelvalue thereof approaches a predetermined target value.

Conversely, in order to raise the contrast, the light intensity maypreferably be lowered for a dark portion (low-reflectance portion), andmay preferably be raised for a bright portion. In other words, the lightintensity is set according to the brightness of the illumination target.That is to say, the light intensity is raised according to an increasein the brightness of an object, and is lowered according to a reductionin the brightness thereof. That is to say, each individual region of thelight distribution pattern may preferably be adjusted such that thelight intensity is lowered according to a reduction in the pixel valuesof the corresponding pixels of the initial image data IMG₁, and israised according to an increase in the pixel values. In the presentspecification, this processing will be referred to as “high-contrastcontrol”. FIG. 14B is a diagram for explaining the high-contrastcontrol. The high-contrast control provides an increase in thebrightness difference between a dark portion and a bright portion. Aview having a large brightness difference has an advantage of allowingthe human eye to recognize the position and the shape of an objectinstantaneously. In addition to the high-contrast control based on amonotonically increasing linear function, the high-contrast control maybe provided based on a monotonically increasing stepwise function asindicated by the broken line. Also, the high-contrast control may beprovided based on a nonlinear function as indicated by the curve ofalternately long and short dashes.

FIG. 15 is a diagram for explaining the image processing according tothe second example. Description will be made below regarding anarrangement in which the low-contrast control shown in FIG. 14A isprovided by gradation inversion. For example, with the maximum gradationas MAX, and with the pixel value of a given pixel as X, the invertedgradation Y is represented by the following Expression.

Y=MAX−X

In a case in which the initial image data IMG₁ is directly subjected togradation inversion, the low-gradation range is displaced to thehigh-gradation range. Accordingly, the noise included in thelow-gradation range of the initial image data IMG₁ is shifted to thehigh-intensity range, leading to noticeable noise (without rounding, asshown in the upper-right graph in FIG. 15). Specifically, dark spots dueto noise are included in the bright region of the light distributionpattern, leading to the potential to degrade the visibility.

In order to solve such a problem, instead of subjecting the initialimage data IMG₁ to gradation inversion without preprocessing, theintermediate image data IMG₂ is generated based on the initial imagedata IMG₁ such that the pixel values in the low-gradation range (0 to A)are rounded, and the intermediate image data IMG₂ is subjected togradation inversion. This allows noise to be reduced in a high lightintensity range (with rounding, as shown in the lower-right graph inFIG. 15).

In summary, the following technical idea can be derived. That is to say,the image processing unit 221 may preferably determine the predeterminedrange RNG so as to reduce noise included in the light intensity rangewhere noise is noticeable in the light intensity distribution. With thepixel value as X, and with the corresponding light intensity as Y, therelation between them can be assumed to be represented by an arbitraryfunction.

Y=f(x)

In this case, in a case in which the light intensity distributionincludes noise, with the upper limit and the lower limit of the lightintensity range where the noise becomes noticeable as Y_(MAX); andY_(MIN), the pixel values X_(MAX) and X_(MIN) that respectivelycorrespond to Y_(MAX) and Y_(MIN) are represented by the followingExpressions.

X _(MAX) =f ⁻¹ (Y _(MAX))

X _(MIN) =f ⁻¹ (Y _(MIN))

Here, f⁻¹ represents the inverse function of the function f.Accordingly, the upper limit and the lower limit of the predeterminedrange may preferably be determined to be) X_(MAX) and X_(MIN),respectively. It should be noted that, in some cases, the relationX_(MAX)>X_(MIN) holds true. Also, in some cases, the relationX_(MAX)<X_(MIN) holds true.

THIRD EXAMPLE

Description will be made regarding another example of the contrastcontrol. FIGS. 16A and 16B are diagrams for explaining the contrastcontrol according to a third example. FIG. 16A shows the relationbetween the reflectance (%) of an object and the brightness. In a casein which light is emitted with a constant light intensity independent ofthe subject, as shown in (i), a proportional relation holds true betweenthe brightness of the object and the reflectance. A “high-contrastimage” as used in the so-called image processing field has a gradationdistribution as shown in (ii). In some cases, a low-contrast image has agradation distribution as shown in (iii).

FIG. 16B shows the relation between the reflectance of an object and thelight intensity (normalized relative value). The reflectance of theobject can be represented by the pixel value. In both the high-contrastcontrol and the low-contrast control, the relation between thereflectance and the light intensity has a large slope in a range wherethe reflectance is low. This means that the noise amplitude is amplifiedin a low-gradation range of the pixel values. Accordingly, in a case inwhich the contrast control is performed as shown in FIG. 16A, thelow-gradation range may preferably be set to the predetermined range RNGwhere the rounding is to be performed before generating the intermediateimage data IMG₂.

In summary, the following technical idea can be derived. That is to say,with the image processing unit 221, in a case in which there is agradation range where the noise amplitude is amplified, the gradationrange may preferably be set to the predetermined range RNG before thelight intensity is calculated (using a function) based on the pixelvalues.

With the pixel value as X, and with the light intensity that correspondsto the pixel value X as Y, the relation between them is assumed to berepresented by an arbitrary function.

Y=f(X)

The range where noise is amplified with a high amplification factor is arange where the function f(X) has a large slope. Such a rangecorresponds to a range where the differential function f′(X) has a largeabsolute value. Accordingly, with the pixel value that provides themaximum value of the slope |f′(X)| as) X_(MAX), the predetermined rangeRNG may preferably be determined such that it includes the pixel valueX_(MAX).

Description has been made above regarding an aspect of the presentinvention based on the second embodiment. Next, description will be maderegarding modifications relating to the second embodiment.

Modification 1

Description has been made in the embodiments regarding a countermeasurefor suppressing noise mainly from the viewpoint of the driver. However,the present invention is not restricted to such an arrangement. It isimportant for automated driving or semi-automated driving to detect atarget by means of an in-vehicle camera. Accordingly, the predeterminedrange RNG where rounding is to be performed may be determined so as toreduce undesired noise from the viewpoint of the in-vehicle camera.

Modification 2

Description has been made in the embodiments regarding an example inwhich, when a bright region of the light distribution pattern includesdark spots due to noise, this leads to degradation of visibility.However, the present invention is not restricted to such an arrangement.The human eye has higher sensitivity for a change in brightness in adark region than for a change in brightness in a bright region. Fromthis viewpoint, when a dark region of the light distribution patternincludes bright spots due to noise, in some cases, such a lightdistribution pattern is unpleasant. Accordingly, in this case, thepredetermined range RNG may preferably be determined so as to reducenoise included in a dark gradation range where the light intensity islow.

Modification 3

Description has been made in the embodiments regarding an example inwhich, as the rounding processing for reducing the number of gradations,bit rounding down (rounding up) is employed. However, the presentinvention is not restricted to such an arrangement. When a pixel valueis included within the predetermined range RNG, the pixel value may bemultiplied by a coefficient that is smaller than 1 so as to reduce theeffective number of gradations. This processing is effective in a casein which the predetermined range RNG is configured as a low-gradationrange.

Description has been made regarding the present invention with referenceto the embodiments using specific terms. However, the above-describedembodiments show only an aspect of the mechanisms and applications ofthe present invention. Rather, various modifications and various changesin the layout can be made without departing from the spirit and scope ofthe present invention defined in appended claims.

What is claimed is:
 1. An automotive lamp adaptive to control a lightdistribution pattern based on an image captured by a camera, andadaptive to switch a plurality of control modes with differentcombinations of a spatial resolution of the light distribution patternand an update speed of the light distribution pattern.
 2. The automotivelamp according to claim 1, wherein the plurality of control modesinclude a first mode in which the light distribution pattern isgenerated with relatively high resolution and relatively low speed, anda second mode in which the light distribution pattern is generated withrelatively low resolution and relatively high speed.
 3. The automotivelamp according to claim 1, wherein the control mode is adaptivelyselected according to a driving environment.
 4. The automotive lampaccording to claim 1, wherein the control mode is adaptively selectedaccording to environmental illumination.
 5. The automotive lampaccording to claim 4, wherein the environmental illumination is detectedbased on the image captured by the camera.
 6. The automotive lampaccording to claim 1, wherein the control mode is adaptively selectedaccording to a driving speed.
 7. The automotive lamp according to claim1, wherein the control mode is adaptively selected according to a speedof an illumination target.
 8. The automotive lamp according to claim 1,wherein the control mode is selected based on a spatial frequency of theimage captured by the camera.
 9. The automotive lamp according to claim1, wherein the control mode is adaptively selected based on a kind of aroad on which a user's vehicle is traveling.
 10. The automotive lampaccording to claim 1, wherein the image captured by the camera isdivided into a plurality of sub-regions, and wherein the control mode isset for each sub-region.
 11. An automotive lamp comprising: a lightdistribution pattern generator structured to generate a lightdistribution pattern based on an image captured by a camera; a lightsource unit structured to emit light to a region ahead of a vehicleaccording to the light distribution pattern; and a mode controllerstructured to adaptively control a combination of a spatial resolutionof the light distribution pattern and an update speed at which the lightdistribution pattern is updated.
 12. A control apparatus for anautomotive lamp, comprising: an image processing unit structured toreceive initial image data captured by a camera, to generateintermediate image data that corresponds to the initial image data, andto generate light intensity control data that determines a lightintensity distribution to be provided by the automotive lamp based onthe intermediate image data, wherein an effective number of gradationsto be used in the intermediate image data is determined for each pixelsuch that it is smaller than a number of gradations used in the initialimage data when a pixel value of the corresponding pixel of the initialimage data is within a predetermined range.
 13. The control apparatusfor the automotive lamp according to claim 12, wherein the imageprocessing unit converts the pixel value into a light intensity, andwherein the predetermined range is determined so as to reduce noiseincluded in a light intensity range where the noise is noticeable in thelight intensity distribution.
 14. The control apparatus for theautomotive lamp according to claim 12, wherein the image processing unitconverts the pixel value into a light intensity, and wherein thepredetermined range is set to a gradation range in which a slope of thelight intensity with respect to the pixel value exhibits a maximum valuethereof.
 15. The control apparatus for the automotive lamp according toclaim 12, wherein processing for generating the light intensity controldata includes comparing a pixel value of the intermediate image data orimage data generated based on the intermediate image data with athreshold value, and wherein the predetermined range is determinedaccording to the threshold value.
 16. The control apparatus for theautomotive lamp according to claim 12, wherein processing for generatingthe light intensity control data includes changing a contrast of theintermediate image data or image data generated based on theintermediate image data.
 17. The control apparatus for the automotivelamp according to claim 12, wherein processing for generating the lightintensity control data includes gradation inversion of the pixel valuesof the intermediate image data or image data generated based on theintermediate image data.
 18. The control apparatus for the automotivelamp according to claim 12, wherein processing for generating theintermediate image data includes rounding lower N bits (N represents aninteger of 1 or more) of the pixel values of the initial image data. 19.The control apparatus for the automotive lamp according to claim 12,wherein processing for generating the intermediate image data includesmultiplying each pixel value of the initial image data by a coefficientthat is smaller than
 1. 20. The control apparatus for the automotivelamp according to claim 12, wherein the image processing unit changes adegree of reducing the number of gradations according to an amplitude ofnoise included in the initial image data.
 21. An in-vehicle controldevice including the control apparatus according to claim
 12. 22. Acontrol method for an automotive lamp comprising: generatingintermediate image data that corresponds to initial image data capturedby a camera; and generating light intensity control data that determinesa light intensity distribution to be provided by the automotive lampbased on the intermediate image data, wherein an effective number ofgradations to be used in the intermediate image data is determined foreach pixel such that it is smaller than a number of gradations used inthe initial image data when a pixel value of the corresponding pixel ofthe initial image data is within a predetermined range.